Landscape Photography is a single viewpoint of a larger nature scene. The subject of a landscape photography image is the scenery. In a landscape photo, persons or animals are not usually featured. Sometimes they are used to represent scale, but are not featured in the composition.
Amongst photographers it is often debated whether man made structures, cities or coastal subjects are representative of landscape photography. Often times these subjects are categorized in different genres, such as Seascape Photography and Cityscape Photography. From a technical standpoint, there is validity to this argument in that landscape photography is a sub genre of Nature photography and man made structures are not natural. However Seascape Photography is definitely a sub genre of nature photography and could be considered a cousin of landscape photography. Another point to consider is that if a landscape photo contains a man made structure in it, such as a road or farm house, is it not still a landscape photo?
Photos of cityscapes and other man made structures are often referred to as urban landscape photography. Oddly enough, photographers practice many of the same principles in their urban photo composition as they use in landscape photography.
Such compositional tools as shape, color, horizon placement and scale are applied to all the different spacial forms of photography. When you break the genres down, the different genres have a lot more in common than they don’t have in common.
All in all, I think it is safe to say that this is a discussion with know clear boundaries that will probably continue on amongst photographers for a long time to come.